1. Field of the Invention
This invention relates to a developing apparatus for use in an image forming apparatus such as a copying apparatus, a printer or a facsimile apparatus.
2. Related Background Art
A color laser printer will be exemplified and briefly described as a conventional electrophotographic image forming apparatus. The surface of an electrophotographic photosensitive body uniformly charged by a primary charging device is exposed by the condensing of a laser corresponding to an image signal by a scanner portion and an electrostatic latent image of each color is formed thereon.
A developing device is disposed at a location opposed to the electrophotographic photosensitive body and at this location, a developing sleeve which is a developer bearing body is positioned so as to be opposed to the surface of the electrophotographic photosensitive body with a minute interval secured therebetween. During image formation, the high voltage source of the main body of the apparatus is connected to the developing sleeve of the developing device and a bias is applied to the latter. At the same time, it is coupled to driving means from the drive source of the main body of the apparatus. By the developing sleeve receiving the application of the bias and rotative driving as described above, the electrostatic latent images on the electrophotographic photosensitive body are developed and toner images are formed.
This developing device is provided with the developing sleeve bearing a toner thereon, a developing blade which is a regulating member adapted to be urged against the outer peripheral surface of the developing sleeve and regulate the thickness of the coat layer of the toner borne on the developing sleeve, and an end seal as a leakage preventing member for preventing the leakage of the toner disposed at the opposite sides of an opening in a developing container for supplying the toner to the developing sleeve.
The opposite ends of the developing blade are of an obliquely cut shape, and a portion of the obliquely cut portion is disposed in overlapping relationship with the aforedescribed end seal. This end seal is stuck on the opposite sides of the opening in the developing container along the circumference of the developing sleeve, and is urged against the developing sleeve with a predetermined amount of crushing to thereby prevent the leakage of the toner to the outside of the toner.
In the above-described prior-art construction, however, that portion of the developing blade which overlaps the end seal, as compared with the other portions, becomes high in the abutting pressure with the developing sleeve by an amount corresponding to the repulsive force by the end seal being crushed. Thereby, the abutting pressure of the developing blade is not uniform and therefore, the developing blade causes minute waving deformation in the lengthwise direction thereof or because of the greater pressure of contact of the developing blade than necessary, the cohesion of the toner is liable to be caused and further, the coherer may be fused on the developing blade and disturb the coat on the developing sleeve, whereby the toner coat layer on the developing sleeve may become non-uniform and good image formation may not be accomplished.